Altec 1220 Schematic ?
« on: January 10, 2017, 03:55:38 PM »
Hello ..   im in the process of putting a 1220 back up to condition. Since i don't have a schematic there's boards and details im not sure of.  Main problem is monitors a b   seems to be the portion on the main board that buzzes  but lacking a schem , i can't really investigate without loosing a lot of time.  I looked on this forum , someone said that he had scanned the schematic , but the adress he fave is returning 404 . so    If anyone would have a diagram for this one , i'd appreciate getting a copy , a scan , photo .. anything that can help will be gladly appreciated ..

thank you



gar381

Re: Altec 1220 Schematic ?
« Reply #1 on: January 14, 2017, 04:00:28 PM »
Fuzzy

This may help you some...

https://www.manualslib.com/manual/365507/Altec-1220-Mixing-Console.html

At least there are flow charts here.
 
The circuits themselves in this Desk are simple and should be an easy reverse.

Best

GARY
RETIRED.....  from 51yrs in Show Biz

gar2520, gar1731,garAM10,gar918 DOAs at  http://capi-gear.com/catalog/index.php?cPath=71_72
NEW Sphere section  http://gar381interests.com/gar381interests.html

Re: Altec 1220 Schematic ?
« Reply #2 on: January 16, 2017, 12:32:33 PM »
Thanks for the URL  , it's the user manual .. and yes .. some kind of flow diagram but not the unbelievably hard to locate schematic  :)   


kpearsall

Re: Altec 1220 Schematic ?
« Reply #3 on: February 07, 2017, 08:08:57 AM »
I've got what you need, at least in hard copy. Whole service manual. Shot me a reminder PM and I'll see if I can get it scanned in or find my digital copy

Re: Altec 1220 Schematic ?
« Reply #4 on: February 22, 2017, 06:20:56 PM »
Thanks for the offer to scan ,  i can really use a diagram which is i have to say , very hard to find

thanks  :)


kpearsall

Re: Altec 1220 Schematic ?
« Reply #5 on: February 23, 2017, 05:56:45 PM »
Sent to your email. Anything I can do to help further? I fixed mine with those documents and can take measurements or anything else you need.

ruffrecords

Re: Altec 1220 Schematic ?
« Reply #6 on: February 24, 2017, 04:09:35 AM »
Sent to your email. Anything I can do to help further? I fixed mine with those documents and can take measurements or anything else you need.

You could always post it to the technical documents section so anyone can access it?

Cheers

Ian
www.customtubeconsoles.com
https://mark3vtm.blogspot.co.uk/
www.eztubemixer.blogspot.co.uk


'The only people not making mistakes are the people doing nothing'

Re: Altec 1220 Schematic ?
« Reply #7 on: February 24, 2017, 08:24:22 AM »
kpearsall :  thank you for the diagrams .Man this is gold.  Again thanks.  now .. time to fix the board.
ok ..   so i done a booboo  :D     looking at the diagram   i see at least one mistake i done.  got the load of the relays post the regulator used for the output 380's  ,  it's time to disassemble  for the fix . i got hum in the audio of ALL outputs     certainly sounds in the ballpark ..
« Last Edit: February 25, 2017, 07:48:35 AM by Fuzzy TheBear »

Re: Altec 1220 Schematic ?
« Reply #8 on: February 24, 2017, 08:37:46 AM »
NOTE : there's a different regulator arrangement on board versus schematic.
On my board version the dimmer transistor is a 2n3055  ( diagram says 40934  which is a 3055 according to tech letter 175a   http://alteclansingunofficial.nlenet.net/publications/techletters/TL_175A.pdf     that's fine   but the b+ for the lm380's is  coming the emitter of an  AL-5367  that is a  2N5367  according to same , the IC is a 7805CT 5volt regulator from Motorola instead of a UA-7824 24volt , also note a piggyback added 120k 10% resistor on R22  .

This is an important difference and i thought enough of a departure to raise a flag.
« Last Edit: February 25, 2017, 08:47:55 AM by Fuzzy TheBear »

kpearsall

Re: Altec 1220 Schematic ?
« Reply #9 on: February 27, 2017, 12:11:43 PM »
You could always post it to the technical documents section so anyone can access it?

Cheers

Ian

I would like to, but I bought them and some of the pages are watermarked. Wouldn't want that company to take issue with us.


Re: Altec 1220 Schematic ?
« Reply #10 on: April 08, 2017, 12:54:08 PM »
Where are we now ?  It's been a while and took a bit of an effort to take this board back to speed but it's design at places totally sucks. I dont know why they made such poor signal flow choices.
a) post fade monitor   b) mic level inputs only      the channel faders never gets to 0 really ..  so there's quite a few bugs with it's design.  What i did do first was take it in pieces and even without looking replace ALL the electrolytics with good grade new parts.  ALL of them . Second mission  : replace all the lightbulbs in all 12 meters.  Third mission : check all resistors , unsolder one side , measure and replace , i had bunches of them off their value by more than tolerance so that got also canned, long tedious , yes .. worth it , absolutely.
The 4 th mission was to invent a way to get line levels to work so i made a series of 10 modules . Each module is a simple 4 pole 2 direction pc mount relay.  What i do is simply switch in a -20 db pad. Each channel has a switch and status led just above the vu meter. They need power on their own. You cannot use the internal power for this, draws too much, so i added a small 24 v psu  and transformer.  I mounted the small pc boards for the relays just at the back of the xlr connector held solid in place.  Wiring is minimal and no signal travels anywhere , just the 24volt to actuate the individual relays.  That took care of the issue and line levels is ok now.  The next one was a bit more ambitious.  Give it a real pre fade listen system.  The first issue here is ok , you want switches to activate PFL .. but where to put them ?  After carefull consideration i decided to mount them between the 2 sets of monitor select switches . It's crowded by 4 10k resistors. and thickness overall available for a push button impossible.  I managed by switching the resistors from component side to solder side , then drill baby drill .  I opted to get the signal right off the input transformer pc board.  ( the following is less than optimal but it worked )  I took every line and took them to a new pc board , 2 uf cap and 10k resistor ,  made 2 buses ( 1 and 2 are separate , allows stereo ) and each of the lines are switched in/out from the new front panel switches ( i used molex 2 pins  on each so i can take modules out without undoing everything. This in turn feeds a  volume control , and switching for mon 1 2 out/ preface listen  and feeds the 30w/channel power amp module and it's own supply .
The switches and volume control are sitting nice between channel 10's vu and the Master VU , with a suitable red button , it's hard to notice it's not original.  I switched around a lot of jacks at the back to have a second mon 1 ,2 output  and have 2 jacks for headphones. the crossover outputs were the easy target.

Think of the 1220 as a good mixer to fiddle around with .. i would not do what i did to a SSL or a Midas .. but hell it's good fun for the bucks . Also it's , once put to speed , an ok board to webcast with . I made a small adapter module for a telephone line that sits outside the board , i didnt want it in .Two 600 ohm transformers few resistors few zeners in a small metal box is all it takes.  So basically the new setup has 2 cd players , computer  ( that's 3 strips )   Strip 1 is main mic + guest mic , Second strip is telephone line and the mic on the DT-109 headphones i am using.  Works out ok .   Got a second computer doing the actual web streaming .   Just having fun with an oldie. 

Re: Altec 1220 Schematic ?
« Reply #11 on: August 05, 2018, 10:54:26 AM »
For anyone looking, I bought and decided to post the service manual. 

You're welcome.